This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A248715 #18 Jul 19 2017 03:04:39 %S A248715 1,10,12,15,17,19,21,23,31,48,50,52,54,60,62,64,67,69,71,73,75,77,89, %T A248715 91,93,101,118,120,122,124,126,128,138,140,142,148,150,152,154,156, %U A248715 159,161,163,179,181,183,185,187,195,197,199,211,220,222,224,226,228 %N A248715 Isolated numbers: Mark the lowest number that doesn't touch a number that has already been mark on grid of number spiraling outward. %C A248715 Start by creating a grid of integers starting with 1 in the center and spiraling outward. %C A248715 . %C A248715 64--63--62--61--60--59--58--57 %C A248715 | %C A248715 37--36--35--34--33--32--31 56 %C A248715 | | | %C A248715 38 17--16--15--14--13 30 55 %C A248715 | | | | | %C A248715 39 18 5---4---3 12 29 54 %C A248715 | | | | | | | %C A248715 40 19 6 1---2 11 28 53 %C A248715 | | | | | | %C A248715 41 20 7---8---9--10 27 52 %C A248715 | | | | %C A248715 42 21--22--23--24--25--26 51 %C A248715 | | %C A248715 43--44--45--46--47--48--49--50 %C A248715 . %C A248715 Then starting with 1 mark all numbers that have no neighboring marked numbers. %C A248715 . %C A248715 . 64 __ 62 __ 60 __ __ __ %C A248715 . %C A248715 . __ __ __ __ __ __ 31 __ %C A248715 . %C A248715 . __ 17 __ 15 __ __ __ __ %C A248715 . %C A248715 . __ __ __ __ __ 12 __ 54 %C A248715 . %C A248715 . __ 19 __ 1 __ __ __ __ %C A248715 . %C A248715 . __ __ __ __ __ 10 __ 52 %C A248715 . %C A248715 . __ 21 __ 23 __ __ __ __ %C A248715 . %C A248715 . __ __ __ __ __ 48 __ 50 %H A248715 Michael P. Tilley, <a href="/A248715/b248715.txt">Table of n, a(n) for n = 1..10383</a> %H A248715 Michael P. Tilley, <a href="/A248715/a248715.png">Image of a 204 X 204 grid </a> %K A248715 nonn %O A248715 1,2 %A A248715 _Michael P. Tilley_, Oct 12 2014